Introduce cairo_has_current_point()

cairo_has_current_point() can be used to determine whether a current
point is defined. We introduce this new symbol with a boolean return
value to avoid the versioning ambiguity of modifying
cairo_get_current_point(). This way we also don't have to map what
should be a routine operation to an error condition as was previously
proposed.

doc/public/cairo-sections.txt

@@ -322,6 +322,7 @@ cairo_copy_path
 cairo_copy_path_flat
 cairo_path_destroy
 cairo_append_path
+cairo_has_current_point
 cairo_get_current_point
 cairo_new_path
 cairo_new_sub_path

src/cairo.c

@@ -3244,6 +3244,26 @@ cairo_get_antialias (cairo_t *cr)
     return _cairo_gstate_get_antialias (cr->gstate);
 }
 
+/**
+ * cairo_has_current_point:
+ * @cr: a cairo context
+ *
+ * Returns whether a current point is defined on the current path.
+ * See cairo_get_current_point() for details on the current point.
+ *
+ * Return value: whether a current point is defined.
+ *
+ * Since: 1.6
+ **/
+cairo_bool_t
+cairo_has_current_point (cairo_t *cr)
+{
+    if (cr->status)
+    return FALSE;
+
+    return cr->path->has_current_point;
+}
+
 /**
  * cairo_get_current_point:
  * @cr: a cairo context
@@ -3254,8 +3274,9 @@ cairo_get_antialias (cairo_t *cr)
  * conceptually the final point reached by the path so far.
  *
  * The current point is returned in the user-space coordinate
- * system. If there is no defined current point then @x and @y will
- * both be set to 0.0.
+ * system. If there is no defined current point or if @cr is in an
+ * error status, @x and @y will both be set to 0.0. It is possible to
+ * check this in advance with cairo_has_current_point().
  *
  * Most path construction functions alter the current point. See the
  * following for details on how they affect the current point:

src/cairo.h

@@ -1276,6 +1276,9 @@ cairo_get_tolerance (cairo_t *cr);
 cairo_public cairo_antialias_t
 cairo_get_antialias (cairo_t *cr);
 
+cairo_public cairo_bool_t
+cairo_has_current_point (cairo_t *cr);
+
 cairo_public void
 cairo_get_current_point (cairo_t *cr, double *x, double *y);